Experimental study on the impact of continuous and dynamic artificial light at night on moths originating from different skyglow conditions.

Biodiversity is negatively affected by light pollution, caused by artificial light at night (ALAN). Light-emitting diodes facilitate new lighting technologies to mediate the negative effects of ALAN, such as dynamic ALAN where light intensity can be adjusted to traffic density. Organisms living in highly light-polluted areas may show adaptations to mitigate the negative effects of ALAN. In a split-brood rearing experiment, larvae of two moth species (Ochropleura plecta and Agrotis exclamationis) originating from low-medium and high-medium skyglow populations were grown under either continuous ALAN, dynamic ALAN or control-dark conditions. We tested for ALAN effects on larval mortality, feeding behaviour, development and body mass, and whether effects depended on skyglow levels in the population of origin. Contrary to previous studies, we found either no or positive effects of ALAN on larval development, with similar or stronger effects of dynamic ALAN compared to continuous ALAN. For A. exclamationis, we showed evidence for faster development, increased growth rate and higher body mass under ALAN. This could reduce larval exposure to parasites and increase fecundity. We found no evidence for evolutionary responses in low-medium or high-medium skyglow larvae. Our results show that ALAN does not affect larval development the same way in all species.